/* Reset and Base Styles */
@import url('https://fonts.googleapis.com/css2?family=Outfit:wght@100..900&display=swap');
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Color Scheme */
    --primary-blue: #2563eb;
    --secondary-green: #10b981;
    --warning-yellow: #f59e0b;
    --danger-red: #ef4444;
    --info-purple: #8b5cf6;
    --neutral-gray: #6b7280;
    --light-bg: #f9fafb;
    --white: #ffffff;
    --text-primary: #1f2937;
    --text-secondary: #4b5563;
    --border-color: #e5e7eb;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
}

body {
    font-family: 'Outfit', sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--light-bg);
}

/* Navigation */
.main-nav {
    background: var(--white);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 90vw;
    margin: 0 auto;
    padding: var(--spacing-sm) var(--spacing-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo h1, .logo a {
    font-size: 1.5rem;
    color: var(--primary-blue);
    text-decoration: none;
    font-weight: 700;
}

.nav-menu {
    display: flex;
    gap: var(--spacing-md);
}

.nav-item {
    position: relative;
}

.nav-link {
    color: var(--text-primary);
    text-decoration: none;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: 0.375rem;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.nav-link:hover {
    background: var(--light-bg);
    color: var(--primary-blue);
}

.dropdown {
    position: absolute;
    top: 100%;
    left: 0;
    background: var(--white);
    border: 1px solid var(--border-color);
    border-radius: 0.5rem;
    min-width: 200px;
    box-shadow: var(--shadow-lg);
    display: none;
    margin-top: 0; /* Remove the gap */
    padding-top: 0.5rem; /* Add spacing inside the dropdown */
    padding-bottom: 0.5rem; /* Optional: Balance the padding */
}

.nav-item:hover .dropdown {
    display: block;
}

.dropdown-item {
    display: block;
    padding: var(--spacing-xs) var(--spacing-sm);
    color: var(--text-primary);
    text-decoration: none;
    transition: background 0.2s;
}

.dropdown-item:hover {
    background: var(--light-bg);
    color: var(--primary-blue);
}

/* Hamburger Menu */
.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--text-primary);
    margin: 3px 0;
    transition: 0.3s;
}

/* Landing Page */
.hero {
    text-align: center;
    padding: var(--spacing-xl) var(--spacing-md);
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--info-purple) 100%);
    color: var(--white);
    margin-bottom: var(--spacing-xl);
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-sm);
}

.subjects-grid {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.subject-card {
    background: var(--white);
    border-radius: 0.75rem;
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-md);
    transition: transform 0.2s, box-shadow 0.2s;
    cursor: pointer;
}

.subject-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.subject-icon {
    width: 60px;
    height: 60px;
    border-radius: 0.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    margin-bottom: var(--spacing-sm);
}

.subject-card h2 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
}

.subject-card p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

.chapter-count {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: var(--light-bg);
    border-radius: 1rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Chapter Layout */
.chapter-container {
    display: flex;
    max-width: 100vw;
    margin: 0 auto;
    min-height: calc(100vh - 60px);
}

.sidebar {
    width: 250px;
    background: var(--white);
    padding: var(--spacing-md);
    border-right: 1px solid var(--border-color);
    position: sticky;
    top: 60px;
    height: calc(100vh - 60px);
    overflow-y: auto;
}

.sidebar h3 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
    font-size: 1.1rem;
}

.section-links a {
    display: block;
    padding: var(--spacing-xs);
    color: var(--text-secondary);
    text-decoration: none;
    border-left: 3px solid transparent;
    transition: all 0.2s;
    margin-bottom: 0.25rem;
}

.section-links a:hover,
.section-links a.active {
    color: var(--primary-blue);
    border-left-color: var(--primary-blue);
    background: var(--light-bg);
}

.chapter-main {
    flex: 1;
    padding: var(--spacing-lg);
    max-width: 1400px;
    margin: 0 auto;
    min-width: 0;
}

.breadcrumb {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    font-size: 0.875rem;
}

.breadcrumb a {
    color: var(--primary-blue);
    text-decoration: none;
}

.chapter-title {
    color: var(--text-primary);
    margin-bottom: var(--spacing-lg);
    font-size: 2rem;
    border-bottom: 2px solid var(--border-color);
    padding-bottom: var(--spacing-sm);
}

/* Content Sections */
.content-section {
    margin-bottom: var(--spacing-xl);
}

.section-title {
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
    font-size: 1.5rem;
}

.content-block {
    background: var(--white);
    padding: var(--spacing-md);
    border-radius: 0.5rem;
    margin-bottom: var(--spacing-md);
}

.info-block {
    border-left: 4px solid var(--primary-blue);
}

/* Concept Cards */
.concept-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

.concept-card {
    background: var(--white);
    padding: var(--spacing-md);
    border-radius: 0.5rem;
    box-shadow: var(--shadow-sm);
}

.primary-concept {
    border-top: 3px solid var(--primary-blue);
}

.secondary-concept {
    border-top: 3px solid var(--secondary-green);
}

.concept-card h3 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
}

.example-block {
    background: var(--white);
    padding: var(--spacing-md);
    border-radius: 0.5rem;
    margin-bottom: var(--spacing-md);
    max-width: 100%;
    /* This creates a new formatting context that contains the wide `pre` tag,
       allowing the pre tag's own `overflow-x: auto` to work correctly. */
    display: grid; 
}

/* Code block is correct as is */
.code-block {
    background: #1f2937;
    color: #e5e7eb;
    padding: var(--spacing-md);
    border-radius: 0.375rem;
    overflow-x: auto;
    white-space: pre;
    font-family: 'Courier New', monospace;
}

/* Note Blocks */
.note-block {
    padding: var(--spacing-md);
    border-radius: 0.5rem;
    margin-bottom: var(--spacing-md);
}

.note-block.warning {
    background: #fef3c7;
    border-left: 4px solid var(--warning-yellow);
    color: #92400e;
}

.note-block.tip {
    background: #dbeafe;
    border-left: 4px solid var(--primary-blue);
    color: #1e40af;
}

.note-block.danger {
    background: #fee2e2;
    border-left: 4px solid var(--danger-red);
    color: #991b1b;
}

.note-block.success {
    background: #d1fae5;
    border-left: 4px solid var(--secondary-green);
    color: #065f46;
}

/* Memorization Area */
.memorization-area {
    background: linear-gradient(to right, #fef3c7, #fde68a);
    padding: var(--spacing-lg);
    border-radius: 0.75rem;
    margin-top: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.mem-header {
    color: #78350f;
    margin-bottom: var(--spacing-lg);
    font-size: 1.75rem;
    text-align: center;
}

.mem-section {
    background: var(--white);
    padding: var(--spacing-md);
    border-radius: 0.5rem;
    margin-bottom: var(--spacing-md);
}

.mem-section h3 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
    border-bottom: 2px solid var(--border-color);
    padding-bottom: var(--spacing-xs);
}

/* Term Cards */
.term-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-sm);
}

.term-card {
    background: var(--light-bg);
    padding: var(--spacing-sm);
    border-radius: 0.375rem;
    display: flex;
    flex-direction: column;
}

.term {
    font-weight: 700;
    color: var(--info-purple);
    font-size: 1.1rem;
}

.definition {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-top: 0.25rem;
}

/* Summary List */
.summary-list {
    list-style: none;
    padding: 0;
}

.summary-point {
    padding: var(--spacing-xs) 0;
    padding-left: var(--spacing-md);
    position: relative;
    color: var(--text-primary);
}

.summary-point::before {
    content: "✓";
    position: absolute;
    left: 0;
    color: var(--secondary-green);
    font-weight: bold;
}

/* Fact Grid */
.fact-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-sm);
}

.fact-card {
    background: var(--light-bg);
    padding: var(--spacing-sm);
    border-radius: 0.375rem;
    text-align: center;
}

.fact-label {
    display: block;
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 0.25rem;
}

.fact-value {
    display: block;
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-blue);
}

/* Chapter Navigation */
.chapter-nav {
    display: flex;
    justify-content: space-between;
    margin-top: var(--spacing-xl);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
}

.nav-btn {
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--primary-blue);
    color: var(--white);
    text-decoration: none;
    border-radius: 0.5rem;
    transition: background 0.2s;
}

.nav-btn:hover {
    background: #1d4ed8;
}

.nav-btn.prev-btn {
    background: var(--neutral-gray);
}

.nav-btn.prev-btn:hover {
    background: #4b5563;
}

/* Footer */
footer {
    background: var(--white);
    text-align: center;
    padding: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
}

/* Responsive Design */
@media (max-width: 768px) {
    .hamburger {
        display: flex;
    }
    
    .nav-menu {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        width: 100%;
        background: var(--white);
        box-shadow: var(--shadow-md);
        flex-direction: column;
        padding: var(--spacing-md);
    }
    
    .nav-menu.active {
        display: flex;
    }
    
    .dropdown {
        position: static;
        display: none;
        margin-left: var(--spacing-md);
        box-shadow: none;
        border: none;
        background: var(--light-bg);
    }
    
    .nav-item.active .dropdown {
        display: block;
    }
    
    .chapter-container {
        flex-direction: column;
    }
    
    .sidebar {
        width: 100%;
        position: static;
        height: auto;
        border-right: none;
        border-bottom: 1px solid var(--border-color);
    }
    
    .hero h1 {
        font-size: 2rem;
    }
    
    .subjects-grid {
        grid-template-columns: 1fr;
    }
    
    .concept-cards {
        grid-template-columns: 1fr;
    }
    
    .chapter-nav {
        flex-direction: column;
        gap: var(--spacing-sm);
    }
    
    .nav-btn {
        text-align: center;
    }
}

/* Add this to the end of your css/styles.css file */

.pdf-viewer-container {
    width: 100%;
    /* 80vh means it will take up 80% of the viewport's height */
    height: 80vh; 
    border: 1px solid var(--border-color);
    border-radius: 0.5rem;
    overflow: hidden; /* Hides any extra scrollbars on the container */
    margin-top: var(--spacing-lg);
}

.pdf-viewer-container iframe {
    width: 100%;
    height: 100%;
    border: none; /* Removes the default iframe border */
}